Cathode ray image scanner with magnetic deflection of scanning ray



@flh 3 H. KNOBLAUCH El AL 2,178,374

CATHODE RAY IMAGE SCANNER WITH MAGNETIC DEFLECTION 0F SCANNING RAY Filed NOV. 28, 1936 Fig.1

Patented Oct. 31, 1939 FATS CATHODE RAY IIVIAGE SCANNER WITH MAGNETIG DEFLIECTION F SCANNING RAY Henning Knoblauch and Werner Kluge, Berlin,

Germany,

assignors to Telefunken Gesellschaft fiir Drahtlose Telegraphic m. b. H., Berlin, Germany, a corporation of Germany 1 Claim.

The invention concerns a cathode-ray picture scanner with magnetic ray deflection arrangement, that is a cathode ray tube where a chargeimage produced by photo-electrons is scanned by a cathode ray so that currents may be generated which may be utilized for television purposes. In Braun tubes, such as used for oscillographic purposes or for reception of television picture, it is known in prior art to use a current-conducting wall coating of the glass tube within the deflector coils for the purpose of preventing the formation of wall charges. The prior art has proposed for preventing too strong an attenuation of the deflecting field by such a wall coating to make use of thin metallic films, for instance of silver, which are applied by the evaporation process. Experience has proved however that cathode ray image scanners provided with a metallic coating of this kind have a relatively short life only which is possibly due to a destruction of the photo-layers present in the imagescanning tube. Thus the prior art had to discard the use of thin wall coatings applied by evaporation which as such entails the danger of a charging of the glass wall.

The invention consists in arranging in front and rear of the deflecting coils two electrodes impressed with an equal or approximately equal potential with the result, as could be shown by experiment, that no charges of disturbing size could appear on the glass wall if it is made partly or wholly without metallic coating.

Two embodiments of the invention are illustrated in the drawing in which Fig. 1 shows a mosaic electrode adapted to be scanned by a beam of electrons and in which the deflecting coils are positioned intermediate two anodes maintained at the same potential, while Fig. 2 shows a modification of Fig. 1 wherein a photoelectric cathode is positioned in register with the mosaic electrode and an electron lens is positioned intermediate the mosaic and the photoelectric cathode for projecting an electron image mosaic.

I0 in Fig. 1 represents a glass vessel wherein is disposed a cathode, and in given cases a control grid and an anode, having the reference mark I I. I2 is a further anode impressed with positive potential with respect to that of I I. The deflecting coils for one of the direction of coordinates is designated by I3. In the other coordinate direction the beam can either be deflected also by coils or by means of deflecting plates. Is is a photo-electric mosaic screen, its photo-sensitive side being faced towards anode I2. I5 is an electrode which represents at the same time the anode for the photo-sensitive elements of screen It and the secondary emission anode for the secondary emission of the mosaic elements occurring during the scanning action. This electrode I5 has the same potential as anode I2. This for the reason that it is connected in the interior of the tube with anode I2 by a wire I 6 to which latter is attached a ring of thin metallic sheeting.

Thus, the glass wall located inside the coils is partly uncovered.

In the cathode ray image scanning device shown in Fig. 2 the first anode I! is arranged inside a glass pipe I8 to which is attached the second anode I2 consisting in this case of a pot-like body having the anode opening at its bottom surface. The deflecting coils are again designated by I3, and I5 is a cylindrical electrode which shall be impressed with the same or approximately the same potential as anode I2. Mosaic screen I4 is in this case provided with mosaic elements whose right side is scanned by the scanning ray and whose other side is facing an electron-optic lens I 9 whereby the photo-electrons emitted by a photo-cathode 29 are guided onto the mosaic elements. The picture to be televised is projected on photo-cathode 20 and there is produced in consequence on screen I4 2. charge-image which corresponds to the density distribution of the television picture.

Having described our invention, what we claim is:

A cathode ray transmitting tube comprising a cathode, a control electrode and a first anode, an insulator supporting the first anode in register with said cathode and control electrode, a second anode in register with the first anode and supported from the insulator, a third anode positioned in register with the first and second anode, and spaced more remotely from the first anode than the second anode, connections to the second and third anode to maintain said anodes at substantially zero potential with respect to each other, a photosensitive electrode in register with the three anodes, electromagnetic deflecting means positioned intermediate the second and third anodes, a second photosensitive electrode positioned in register with the first photosensitive electrode and more remote from the cathode than the first photosensitive electrode, and an electron optical lens positioned intermediate the first photosensitive electrode andthe photosensitive element.

HENNING KNOBLAUCH. WERNER KLUGE. 

